Comparison of Postoperative Pulmonary Complication Indices in Elective Abdominal Surgery Patients

Background: Postoperative pulmonary complications (PPC) are important problems that prolong hospital stays by increasing morbidity and mortality of patients. Early identification of risky cases through preoperative evaluation is important for reducing the complications that may be seen in patients postoperatively. The aim of this study is to calculate, evaluate and compare the risk indices for PPC in patients who will undergo elective abdominal surgery. Materials and Methods: One hundred twenty-four patients who were hospitalized for elective abdominal surgery were included in this prospective observational study. American Society of Anesthesiologists (ASA), Epstein and Shapiro scores, respiratory failure index (RFI), pneumonia risk indexes (PI) and scores were calculated preoperatively. Patients were re-evaluated at the 48th postoperative hour, and one-week follow-up was performed. The patients with PPCs are recorded. Results: The mean PPC rate was 36.8%. Based on this, pleural effusion was observed in 18.5%, prolonged mechanical ventilation in 8.9%, atelectasis in 9.7%, and respiratory failure in 5.7%, bronchospasm in 4.0%, and pneumonia in 3.2% of patients. An increased risk in PPC was determined if ASA were above 3 (odds ratio, [OR], 7.06; <0.001), PI scores were above 3 (OR, 6.67; <0.001), RFI score were above 4 (OR, 6.30, p:0.001) and Shapiro score above 2 (OR, 20.01; <0.001), respectively. Conclusion: The Shapiro index is the strongest predictor of pulmonary complications, whereas the PI is the strongest predictor of morbidity risk. However, RFI and the PI are equally valuable for predicting respiratory complications and may prove to be useful in abdominal surgeries for preoperative assessment.


INTRODUCTION
Postoperative pulmonary complications (PPCs) in abdominal surgery are important factors that can prolong the length of hospital stays, as well as be a cause of morbidity and mortality (1). The preoperative assessment (PA) plays an important role in predicting complications and taking precautions, it is often performed to collect history and the results of a physical examination, chest X-ray, respiratory function tests (RFT), as well as arterial blood gas (ABG) and exercise tests, as required (2). The CRI has been used for a long time to detect perioperative cardiac and pulmonary complications. The total score is 10 in the CPRI assessment. The postoperative cardiopulmonary complication rate has been found to be 73.4% in patients with a score greater than 4 and 11% in those with a score less than 4 (4).
The Shapiro index was developed after the ASA and the CPRI and includes parameters defining spirometry, blood gas, cardiovascular system, nervous system, and postoperative recovery period. It can appear to resemble the CPRI but contains different nervous system and muscle strength examinations (5).   Patients were re-evaluated at the 48 th postoperative hour, and a one-week follow-up was performed. The type of operation, its duration, the incision size and shape, and whether or not the operation was performed by laparoscopy were recorded. Extubation time and complications were determined for patients who were in the intensive care unit for more than 48 hours. Respiratory symptoms and physical conditions for all patients were checked. Chest X-rays and arterial blood gas analyses were performed in cases in which the patient showed symptoms or there were pathological examination findings. All postoperative complications (atelectasis, bronchospasm, reintubation, prolonged mechanical ventilation, pleural effusion, respiratory failure, COPD exacerbation, pneumonia, and acute respiratory distress syndrome) were recorded. Definitions were obtained from the "European Perioperative Clinical Outcome Definition" (8). All patients were checked at the end of 1 month, and the survival rate was calculated.

Statistical analysis
The data obtained by the surveys were uploaded to the surgeries were compared to patient and surgery parameters. Factors affecting PPC were assessed using a chi-squared (χ 2 ) analysis, the differences between grouped data were assessed using a student-t test, and the parameters that did not fulfill parametric conditions (determined by measurement) were assessed using the Mann Whitney-U test. The capability to determine the frequency of complications of the indices that determine postoperative complications was calculated using the chisquared (χ 2 ) analysis beneath the curve and by measuring the odds ratios (OR) and the 95% confidence interval, which was calculated using the Miettinen formula. All results were evaluated with a 95% confidence interval and a significance level of p<0.05.

RESULTS
One hundred and twenty-four patients scheduled to undergo elective abdominal surgery were included in the study. Demographic data of patients, distribution of preoperative risk indices, clinical characteristics of patients Respiratory and non-respiratory complications were observed in all patients requiring prolonged postoperative mechanical ventilation. Therefore, the 1-month mortality of these patients was recorded as 54.5%.  There are multiple complications in the same patient. When the PPCs were compared by incision types, there were no statistically significant differences between vertical, horizontal, and subcostal incisions (p>0.05); increase in incision size (p=0.02) and duration of operation (p < 0.001) statistically increased PPC risk. As the fall rate of albumin values in the postoperative period grew higher than that of the preoperative period, the risk of developing PPC also increased (p=0.002).
When the respiratory function tests were compared to the PPC, there was a statistically significant relationship between FEV1, FVC, FEV1 / FVC, FEF25-75, and percentages and the development of PPC (Table 4).

Risk indices and respiratory complications
When the CRI and PRI were evaluated in terms of respiratory complications, the odds ratio was found to be 2.34 (0.16<OR < 4.51) and 3.15 (0.40<OR < 5.89). However, when this index was used with the CPRI, it was observed that a score of 3 and above showed the complications to be much better. When the CPRI was 3 and above, the odds ratio was 9.33 (3.72 < OR < 14.92). The odds ratio was 7.06 (3.10 < OR < 11.01) when ASA was III and above; it was 6.30 (1.76 < OR < 7.56) when the RFI was 4; and it was 6.67 (3.33 < OR < 9.45) when the pneumonia risk index was>3.
The odds ratio was found to be 20.01 (9.30<OR < 30.41) on the Shapiro index of 3 and above, making it the best predictor of respiratory complications ( Table 5). The PPC distribution of all patients according to risk indices is presented in Table 6.

Indices and death
At    In general, PPCs are seen in 5-10% of major abdominal surgeries (7,9). Therefore, pulmonary complications are more common following upper abdomen, thoracic and abdominal aortic aneurysm repair surgeries (10). The incidence of atelectasis in abdominal surgeries is reported to be 20-69%, while postoperative pneumonia is reported to be 9-40% (11). However, it is necessary to perform a preoperative assessment on patients before they undergo surgery and to take necessary precautions to alleviate any potential complications. PPCs are important problems that prolong hospital stays by increasing morbidity and mortality of patients (12 Age is an important factor in the development of PPC. In a relevant study by Djokovic et al., postoperative 30-day mortality was found in 6.2% of patients over 80, and less than 1% of these patients were in the ASA II class (14).
Similarly, we have found that the frequency of complications increases with age.
In a meta-analysis conducted in 2014, PPC was reported that a certain period of learning was required to make patients quit smoking during the preoperative period and that complications occurred in 57% of patients who did not quit, as opposed to those 33% of patients who quit 8 weeks prior to surgery (16). The results obtained here can be used in another study to further investigate preoperative smoking cessation rates according to disease symptoms and to determine how many patients who quit smoking in the pre-operative period continued not to smoke post-operatively.
Although there are contradictory studies regarding the type and size of the incision, it is reported that complications are more common with a vertical incision (1). In a study conducted by Kumar et al. in 2018, no difference was found between the type and size of incisions in abdominal surgeries (17). In our study, no difference was found between the incisions when all the abdominal surgeries were considered, but there were more complications in these three types of incisions than in the Another important point for PPCs is duration of anesthesia and surgery. PPCs had been reported more frequently in surgeries lasting more than 4 hours (9,12,18).
Similarly, in our study, the duration of surgery in cases with PPC were longer than 4 hours (270.56 ± 110.11 min).
Prolonged anesthesia duration causes atelectasis in the lung. In recent years, lung protective low tidal volume ventilation (6-8 ml/kg), and positive-end expiratory pressure (PEEP; 6-8 cm H2O) are preferred to reduce this issue (19). In another study, it has been reported that PPC risk increases with increasing duration of surgery (20). In this study, OR was reported 4.9 (2.4-10.1) and 9.7 (4.7-19.9) in operations over 2 hr and 3 hr, respectively.